Compositions and Methods for the Prevention and Treatment of Diseases in Plants

ABSTRACT

Non-toxic, environmentally friendly, naturally-derived and economical compositions and methods for treating and preventing bacterial or fungal disease in plants, especially disease caused by  Xanthomonas  species, such as citrus canker, wherein such compositions include d-limonene alone or in combination with wax and/or wax extract, monohydric alcohol, an emulsifier and/or other ingredients are provided. Methods of making such compositions are also provided.

CROSS REFERENCE APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.11/093,501 filed on Mar. 30, 2005, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to compositions and methods for thetreatment and prevention of bacterial and fungal disease in plants.Among the important diseases which can be treated and prevented by suchcompositions and methods is citrus canker.

BACKGROUND OF THE INVENTION

As reported by the University of Florida Plant Pathology Department,fungal and bacterial pathogens can lower yields, reduce quality,negatively affect the aesthetic and economic value and even ultimatelydestroy plants, crops, pre-harvest fruits, trees, vegetables andgrasses. In particular, bacterial and fungal diseases in citrus plantscreate huge economic burdens on the citrus industry worldwide. Citruscanker alone causes severe economic consequences in the world's citrusgrowing regions. The bacteria which causes citrus canker, Xanthomonascampestris pv. citri, has been found in southern Asia, Japan, the MiddleEast, Africa, South America and now North America. Historically, citruscanker outbreaks have occurred in North America in the early 1900s andagain in 1986. Fortunately, through the use of aggressive eradicationtechniques, the disease was eliminated in both instances. Citrus canker,however, can be reintroduced when people inadvertantly transportinfected citrus fruits and seedlings into citrus growing areas in theU.S. and elsewhere. In the U.S., Florida is by far the state most atrisk from citrus canker given its combination of high humiditythroughout the year, seasonal hurricanes and frequent thunderstormsaccompanied by high wind gusts. (See The University of Florida PlantPathology Department Report atvvvvw.biotech.ufl.edu/PlantContainment/canker.htm.)

The University of Florida Extension Service reports that in 1995 citruscanker was again detected in the U.S. in citrus trees in the Miami-DadeCounty, Fla. area. Citrus canker then spread to the commercial groves insouthwest Florida. Since 1998 more than 870,000 trees have beendestroyed in conjunction with eradication programs. (Seehttp://edis.ifas.ufl.edu/FE286)

Costs in managing the threat of citrus canker include capital investmentfor spray equipment, the lost value of affected fruit, costs associatedwith inspection and eradication, and costs associated with the creationof natural windbreaks and other defensive tactics. Current sprayingprograms include relatively expensive copper based sprays. TheUniversity of Florida Extension Service has estimated that if citruscanker became endemic in Florida, the total cost for countering endemiccitrus canker, including the use of copper based sprays, could be morethan $300 per acre.

Many types of organic molecules possess antimicrobial properties and canhe used to effectively control fungal and bacterial disease in plants.For example, previous attempts to control such disease in plantsincludes, for example, copper-containing fungicide and streptomycinsprays. Other fungicides, herbicides and pesticides have been used aswell.

However, many of the currently used products are toxic to humans,animals and the exposed environment which limits large scale applicationof such products in, for example, citrus orchards, The EnvironmentalProtection Act was established in 1972, in part, to address concernsover the use of potentially toxic materials to control or treat diseasesin crops. In 1996 Congress passed the Food Quality Protection Actrequiring the Environmental Protection Agency to reassess the safety andefficacy of every existing pesticide by 2006. Concerns about pesticideresidues on plants and the exposure of field workers to such residuesseverely limits the amounts of pesticide that can be applied and thetiming of such application. These limitations decrease the potentialeffectiveness of commonly used pesticides to prevent and treat bacterialand fungal disease in plants in general and citrus canker in particular.

Accordingly, there exists a tremendous need for effective, economicaland non-toxic compositions and methods for preventing and treatingbacterial and fungal disease in plants. In particular there is atremendous need for non-toxic, environmentally friendly, effective andeconomical compositions and methods for preventing and treating citruscanker.

SUMMARY OF THE INVENTION

The present invention provides non-toxic, environmentally friendly,effective and economical compositions and methods which prevent andtreat bacterial and fungal disease in plants. More particularly, thepresent invention is effective in preventing and treating disease causedby the various species of the bacteria Xanthomonas, including diseasessuch as citrus canker. Compositions according to the present inventioninclude d-limonene as the primary active ingredient alone or incombination with wax and/or wax extract, monohydric alcohol and otheringredients. Applicants have unexpectedly found that such compositionsare capable of preventing and treating bacterial and fungal disease inplants, including citrus canker.

Moreover, compositions and methods according to the present inventionare environmentally friendly since they do not include or involve theuse of toxic chemicals or chemicals at toxic levels. Accordingly, thereare minimal regulatory limitations for the use of such compositions.

The present invention also provides methods of making and using suchcompositions.

Accordingly, one object of the present invention is to providecompositions for preventing and treating bacterial and fungal disease inplants, especially diseases caused by Xanthomonas species such as citruscanker, comprising d-limonene alone or in combination with wax and/orwax extract, monohydric alcohol and/or other ingredients.

Another object of the present invention is to provide methods of makingcompositions for preventing and treating bacterial and fungal disease inplants, especially diseases caused by Xanthomonas species such as citruscanker.

A further object of the present invention is to provide methods ofpreventing and treating disease in plants, including diseases caused byXanthomonas species such as citrus canker, which include applyingcompositions described herein to plants.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides non-toxic, naturally-derived,environmentally friendly compositions and methods for treating andpreventing bacterial and fungal diseases, especially disease caused byspecies of the bacteria Xanthomonas such as citrus canker.

The compositions of the present invention may comprise d-limonene aloneor in combination with wax and/or wax extract, monohydric alcohol andother ingredients. Applicants have unexpectedly found that suchcompositions are capable of treating and preventing bacterial and fungaldisease in plants, especially disease caused by Xanthomonas such ascitrus canker. Moreover, such treatments do not create any perceivableconcommitant negative consequences such as, for example, fruitproduction decreases, leaf drop or leaf wilt.

As used herein, unless otherwise stated, percentage amounts of aningredient are by total weight of the composition in which thatingredient is included prior to any dilution of the composition withwater or other diluent and/or prior to any freeze-drying process.

Compositions of the present invention include d-limonene. D-limonene isthe major component of the oil extracted from citrus rind and has beenused extensively as an ingredient in cleaning products. D-limonene incompositions according to the present invention may comprise up to about100% of the non-diluted product. In certain embodiments prior todilution, d-limonene may comprise by weight from about 0.5% to about20.0%, in other embodiments from about 5.0% to about 15.0%, and in otherembodiments from about 9.0% to about 11.0%.

After dilution the weight percentage of d-limonene preferably drops toless than about 50% of the composition, more preferably less than about20%, and most preferably less than about 10%. D-limonene may be presentin diluted compositions in amounts as low as 0.01% by weight. D-limoneneis commercially available from many sources.

Compositions of the present invention also may include wax material,more preferably an extract of wax material. The preferred wax materialis beeswax. Prior to any dilution, the wax and/or wax extract maycomprise from about 0.005% to about 10.0%, preferably from about 0.01%to about 1.0%, and more preferably from about 0.05% to about 0.5% andeven more preferably about 0.1% of the composition. Optionally, as asubstitute for, or in addition to wax and/or wax extract, compositionsaccording to the present invention may include benzoic acid, salicylicacid and paraffin, and/or extracts of any of the above, alone or invarious combinations, in amounts by weight totaling those given abovefor wax and/or wax extract alone.

Extracts of wax may be obtained by heating a wax and water mixture andthen filtering the solution to obtain the extracts. In certainembodiments about 99% of the solids are filtered out leaving asubstantially solid-free wax extract.

After dilution, the wax and/or wax extract may be present in amountsreflecting the degree of dilution. For example, if compositionsaccording to the present invention are diluted prior to use by theinclusion of 3 parts diluent to 1 part concentrated composition, theamount of wax or wax extract will be about 25% of its originalconcentration by weight.

Wax (such as beeswax), benzoic acid, salicylic acid and paraffin arecommercially available from many sources.

Preservative compositions of the present invention also may includeemulsifiers such as soy lecithin. Among the advantages of emulsifierssuch as soy lecithin are surface-active properties which provide, forexample, the reduction in mixing time and the maintenance of stabilityof dispersions. Emulsifiers such as soy lecithin also provide adesirable homogenous appearance and prevent surface separation. Prior todilution, emulsifiers used in the present invention may comprise fromabout 0.05 to about 15%, more preferably from about 0.5 to about 10%,and more preferably from about 1 to about 5%. Lecithins, particularlysoy lecithins are preferred in certain embodiments of the presentinvention. Other ingredients may be used, for example, in amountsdescribed above either alone or in combination with soy lecithin. Forexample, canola oil and/or caprylic acid may be used as emulsifiers.After dilution, the concentration by weight of emusifiers will drop inproportion to the extent of dilution as discussed above. Emulsifierssuch as soy lecithin are commercially available from many sources.

Compositions according to the present invention also may includemonohydric alcohols such as methanol, ethanol and butanol, alone or invarious combinations. A preferred monohydric alcohol is ethanol. Apreferred combination of monohydric alcohols includes ethanol andmethanol. Monohydric alcohols according to the present invention may beeither denatured or non-denatured. Prior to dilution, monohydric alcoholmay comprise from about 0.5% to about 15.0%, more preferably about 2.0to about 12.0%, and even more preferably from about 4.0 to about 9.0% ofthe composition. After dilution, the concentration by weight ofmonohydric alcohol will drop in proportion to the extent of dilution asdiscussed above. Monohydric alcohols are commercially available frommany sources.

Compositions of the present invention also may include other excipients.Other excipients may include potassium hydroxide, xanthan gum, andhydrochloric acid. Potassium hydroxide and hydrochloric acid may be usedto control and adjust pH levels. Xanthan gum may be used to control andadjust viscosity and also provide product stability. When included incompositions according to the present invention prior to dilution,potassium hydroxide may comprise from about 0.01% to about 5.0%, morepreferably from about 0.05% to about 2.0%, and even more preferably fromabout 0.05% to about 0.5% of the composition. When included incompositions according to the present invention, xanthan gum maycomprise from about 0.01% to about 2.0%, preferably from about 0.01% toabout 1.0%, and more preferably from about 0.1% to about 0.5% of thecomposition. After dilution the concentration by weight of theseexcipients, if present, will drop in proportion to the extent ofdilution as discussed above. All of the above-mentioned excipients arecommercially available from many sources.

The balance of undiluted, concentrated forms of compositions accordingto the present invention may comprise water. The water may be purifiedand, if so, preferably has a bacterial colony count of less than about100 colonies per ml. The water may be made alkaline by the addition ofpotassium hydroxide and preferably has a pH above about 10.0. Thepreferred water hardness is less than 1 grain per gallon or less than 50ppm. In certain embodiments water may comprise by weight from about 35%to about 99% of compositions according to the present invention. Asdiscussed previously, extremely concentrated compositions comprising,for example, higher amounts of d-limonene and wax and/or wax extract areintended to be within the scope of the invention. As such, water may bepresent in amounts lower than 35%.

Methods of Making

The present invention also provides methods of making the compositionsdescribed herein. Such methods can be as simple as providingconcentrated forms of d-limonene in a suitable container. Methods alsoinclude combining d-limonene and water.

In another embodiment, compositions according the present invention maybe made by (1) adding monohydric alcohol to water and mixing; (2)heating the alcohol and water mixture; (3) adding d-limonene and mixing;(4) heating the monohydric alcohol, d-limonene and water combination;(5) adding wax and/or wax extract and mixing further; (6) heating themonohydric alcohol, d-limonene, wax and/or wax extract and watermixture; (7) optionally filtering the mixture; and (8) optionallycooling the filtrate.

In another embodiment the method of making compositions includes thesteps of (1) adding potassium hydroxide to water and mixing; (2) addingmonohydric alcohol (e.g., ethanol) to the water and mixing; (3) heatingthe potassium hydroxide, alcohol, and water mixture to about 175° F. forfive minutes or less; (4) adding d-limonene to the water and mixing,while maintaining the temperature at about 175° F. for about 15 minutes(4) adding beeswax and/or beeswax extract to the water and mixing, whilemaintaining the temperature at about 170° F. for about 15 minutes; (5)adding xanthan gum and mixing vigorously while allowing the mixture tocool; (6) filtering the cooled mixture.

In another embodiment methods of making compositions according to thepresent invention may include the steps of (1) mixing water, wax and/orwax extract, and potassium hydroxide in a container; (2) adding to thecontainer d-limonene and an emulsifier, such as soy lecithin, andmixing; and (3) adding to the container a monohydric alcohol and mixing.

In another embodiment, methods of making compositions according to thepresent invention may include the steps of (1) mixing water, beeswaxextract, and potassium hydroxide in a container; (2) adding to thecontainer d-limonene and soy lecithin and mixing; and (3) adding to thecontainer ethanol and mixing.

In yet another embodiment, methods of making compositions according tothe present invention may include the steps of (1) mixing in a containerwater, beeswax extract and potassium hydroxide, wherein water is presentin amounts by weight from about 35% to about 99%, wherein the beeswaxextract is present in amounts by weight from about 0.005% to about10.0%, and wherein potassium hydroxide is present in amounts by weightfrom about 0.01% to about 5.0%; (2) adding to the container d-limoneneand soy lecithin and mixing, wherein the d-limonene is present inamounts by weight from about 0.5% to about 20.0%, and wherein soylecithin is present in amounts by weight from about 0.05 to about 15%;and (3) adding to the container ethanol and mixing, wherein ethanol ispresent in amounts by weight from 0.5% to about 15.0%.

It should be noted that the order of steps recited above in embodimentsof the present invention may be varied to produce compositions accordingto the present invention. For example, d-limonene may be added prior toadding monohydric alcohol or wax and/or wax extract could be addedbefore either d-limonene or monohydric alcohol.

In certain examples of embodiments of the present invention, water maybe heated in any heating step (if the particular method of making thecomposition includes heating water or water and other components) tobetween about 110° to about 272° F., preferably to between about 130° toabout 210° F., and more preferably to between about 165° to about 180°F.

The liquid mixture may then be pumped through filters at a pressuresufficient to effectively collect the composition. The filteringpressure may be from about 5 to about 100 psi, preferably is from about10 to about 40 psi, and more preferably is about 30 psi. The compositionmay be cooled before use. Preferably the composition may be cooled to atleast about 95° F. Cooling may be facilitated by the use of a heatexchanger.

Compositions according to the present invention also may be formed intoa crystalline powder form to facilitate packaging, storage and use. Thismay be achieved, for example, by reducing the water content to about 10%of the composition, adding xanthan gum and gum arabic in roughly equalamounts, drying the composition, and then grinding to break up largerparticles. Drying may be achieved by, for example, a vacuum drier, afluidized bed drier, a low temperature roller drier, a vacuum extrusiondrier or by other drying means.

Methods of Using

The present invention also includes methods of using compositions whichcan prevent and treat bacterial and fungal diseases in plants,especially diseases caused by Xanthomonas species, such as citruscanker. An effective amount of the compositions of the present inventioncan be applied to plants such as citrus trees. In this context aneffective amount means an amount that is sufficient to prevent andreduce bacterial or fungal disease affecting plants such as citruscanker. Accordingly, an effective amount can vary depending on whetherthe primary purpose is prevention or treatment, and if the latter, theseverity of the disease state.

In general, however, compositions according to the present invention maybe effectively applied to citrus trees in a concentration ranging fromabout 1% to about 80%. Preferably, the concentration will be between 10%and 50% and more preferably between 20% and 40%. To achieve suchconcentrations, compositions according to the present invention may bediluted with an appropriate diluent such as water. Other suitablediluents may be used instead of water, although water should be the mosteconomical diluent. Alternatively, compositions according to the presentinvention may be incorporated into existing (or yet to be developed)formulations of herbicides, pesticides and fungicides, including thosecurrently used by commercial growers. One benefit of includingcompositions according to the present invention into certain herbicides,pesticides and/or fungicides is that it may reduce the total amount oftoxic chemicals that would otherwise be applied to plants, includingcitrus trees.

Compositions according to the present invention can be sprayed ontoplants that do not have any observable disease using conventional sprayequipment. Likewise, these compositions can be sprayed onto diseasedplants in the same manner. For use in diseased plants, the concentrationof compositions according to the present invention generally will behigher than for preventative treatments.

Compositions according to the present invention may reduce or eliminatethe growth of a wide-range of disease-causing organisms in plants,including citrus trees. These compositions have been shown to beespecially effective in the treatment and prevention of citrus cankercaused by Xanthomonas, including Xanthomonas campestris pv. Citri, thecausative agent of citrus canker.

In addition to use in citrus species, compositions according to thepresent invention are also effective in treating and preventingbacterial and fungal infections (and/or infestations) in other types ofplants. Such diseases include (but are not limited to) diseases causedby other Xanthomonas species, diseases caused by Pseudomonas, anddiseases caused by other bacteria, as well as fungal diseases anddisease caused by infestation of certain insects.

In addition to citrus plants, compositions and methods according to thepresent invention are also effective in preventing and/or treatingdiseases in tomatoes, bell peppers, grapes and other plants. Forexample, such compositions will be effective in treating and preventingdiseases of tomatoes including bacterial spot, caused by Xanthomonascampestris pv. Vesicatoria. Compositions according to the presentinvention also will be effective in treating and preventing earlyblight, late blight and septoria leaf spot.

Similarly, such compositions will be effective in treating andpreventing disease in bell peppers (and other peppers) such as, forexample, bacterial leaf spot, cercospora leaf spot, southern blight andtobacco mosaic virus.

Compositions according to the present invention also will be effectivein treating and/or preventing diseases associated with the wineindustry. Such diseases include those effecting grapes or vines causedby fungi, such as mildew and various rot conditions, diseases caused bybacteria, such as bacterial blight and Pierce's disease, grapevineyellows disease, and diseases caused by viruses. Compositions accordingto the present invention also will reduce the incidence of Pylloxera.

EXAMPLE 1

The composition as shown in Table 1 was used to demonstrate theeffectiveness of an exemplary embodiment of the present invention intreating citrus canker: TABLE 1 monohydric alcohol (ethanol) 6.65%d-limonene 10.00% beeswax extract 1.47% water 81.40 potassium hydroxide0.16% xanthan gum 0.16%

Ten citrus trees with existing canker lesions were drench sprayed with a25% solution of the composition according to Table 1, while ten citrustrees were used as controls. Tree limbs were tagged with strips ofcaution tape to facilitate precise identification of the treatmenttrees. Weekly observations were taken to determine the effect of thetreatment on the canker lesions. A second treatment was appliedapproximately two weeks after the first. Over the course of eight weeksof observation, canker lesions had not expanded on the ten treatmenttrees, while canker lesions had grown substantially on the ten controltrees. The treatment trees and control trees both exhibited similarinsubstantial levels of leaf wilting and fruit drop.

EXAMPLE 2

In order to more precisely quantify the effectiveness of compositionsaccording to the present invention, compositions in accordance withTable 1 above were tested on cultures of Xanthomonas campestris pv.citrumelo obtained from the Florida Department of Plant Industry,Florida Department of Agriculture & Consumer Services, Gainesville, Fla.

Test Procedures

Xanthomonas was grown via at least two transfers at 30° C. for 48 hr inTryptic Soy broth (TSB). The final culture was centrifuged at 10,000×gfor 10 min., the cells resuspended in sterile Butterfield's phosphatebuffer (BPB) to obtain 10 mL of a suspension with an approximate celldensity of 1×10⁸ CFU/mL. The final working inoculum suspension wasenumerated.

A modification of the AOAC Method 960.09 (Germicidal and DetergentSanitizing Action of Disinfectants) was used to test the disinfectantefficacy of a solution of the composition.

-   -   1) Two flasks containing 99 ml each of the antimicrobial        solution were prepared in sterile 250 ml flasks containing        sterile stir bars. A single flask of control solution (99 ml of        sterile Butterfield's phosphate buffer (BPB) was also prepared.        The flasks were equilibrated to room temperature (22-25° C.)        before initiating the efficacy tests.    -   2) One ml of the inoculum suspension (10⁸ CFU/ml) was inoculated        into each of the flasks while stirring slowly to yield a flask        inoculum level of ca. 10⁶ CFU/ml. The flasks were stirred slowly        during the tests.    -   3) Each flask was sampled 30 sec. after inoculation and        subsequently after 1, 5, and 10 min. of incubation/exposure at        25° C. Flasks were sampled by aseptically transferring a one ml        aliquot to a tube containing 9.0 ml of Difco neutralizing broth        (to yield an initial dilution of 1:10).        Microbial Analysis

Sample aliquots from the initial (10⁻¹) neutralizing tubes were seriallydiluted in BPB and enumerated via surface plating on pre-poured platesof Tryptic Soy agar (CYSA) agar, TSA plates were incubated for 48 h at30° C.

Bacterial counts were expressed as colony forming units per ml of samplesolution and converted to log₁₀ transforms. Log₁₀ mean counts werecalculated for each solution time variable. The log₁₀ reduction andpercentage reduction (versus the control sample after 30 sec.) was alsocalculated for each exposure time.

Results

Compositions according to the present invention were shown to be highlyeffective in reducing Xanthomonas counts. The control (BPB buffer) countof Xanthomonas was 6.11, 6.04, 6.11, and 5.94 log₁₀ CFU/ml of solutionafter 30 sec., 1 min. 5 min., and 10 min., respectively. There was anincreasing reduction of Xanthomonas counts in the test solution as theexposure times increased with significant reductions (i.e., >1 log₁₀CFU/ml) noted after 5 and 10 min. exposure times. There was a 1.98 log₁₀CFU/ml (98.94%) reduction of mean Xanthomonas counts in the testsolution following a 5 min. exposure time and a 4.16 log₁₀ CFU/ml(99.995%) reduction of mean Xanthomonas counts following a 10 min.exposure time.

1. A composition for treating and preventing disease in plants comprising d-limonene.
 2. The composition of claim 1, further comprising wax and/or wax extract.
 3. The composition of claim 2, further comprising monohydric alcohol.
 4. The composition of claim 3, further comprising potassium hydroxide.
 5. The composition of claim 4, further comprising an emulsifier.
 6. The composition of claim 5, wherein the emulsifier is soy lecithin.
 7. The composition of claim 1, wherein d-limonene is present in an amount up to about 50% by weight and wherein said composition further comprises water.
 8. The composition of claim 7, further comprising wax and/or wax extract.
 9. The composition of claim 8, further comprising monohydric alcohol.
 10. The composition of claim 9, further comprising potassium hydroxide.
 11. The composition of claim 10, further comprising an emulsifier.
 12. The composition of claim 11, wherein the emulsifier is soy lecithin.
 13. The composition of claim 7, comprising from about 0.5% to about 20% d-limonene, from about 0.005% to about 5.0% wax and/or wax extract, from about 0.5% to about 15% monohydric alcohol, from about 0.01% to about 5.0% potassium hydroxide, and from about 0.05% to about 15% emulsifier, all by weight.
 14. The composition of claim 13, wherein the monohydric alcohol is selected from the group consisting of ethanol, methanol and butanol, alone or in combination.
 15. The composition of claim 13, wherein the wax and/or wax extract comprises beeswax and/or beeswax extract.
 16. The composition of claim 13, wherein the emulsifier comprises soy lecithin.
 17. The composition of claim 13, wherein the plant is a member of the citrus species.
 18. The composition of claim 17, wherein the disease is citrus canker.
 19. The composition of claim 13, wherein the disease is caused by any species of Xanthomonas.
 20. A method for treating or preventing disease in a plant species comprising applying to said plant species a composition which comprises d-limonene.
 21. The method of claim 20, wherein said composition further comprises wax and/or wax extract.
 22. The method of claim 21, wherein said composition further comprises monohydric alcohol.
 23. The method of claim 22, wherein said composition further comprises potassium hydroxide.
 24. The method of claim 23, wherein said composition further comprises an emulsifier.
 25. The method of claim 24, wherein the emulsifier is soy lecithin.
 26. The method of claim 20, wherein d-limonene is present in an amount up to about 50% by weight and wherein said composition further comprises water.
 27. The method of claim 26, wherein said composition further comprises wax and/or wax extract.
 28. The method of claim 27, wherein said composition further comprises monohydric alcohol.
 29. The method of claim 28, wherein said composition further comprises potassium hydroxide.
 30. The method of claim 29, wherein said composition further comprises an emulsifier.
 31. The method of claim 30, wherein the emulsifier is soy lecithin.
 32. The method of claim 26, wherein said composition comprises from about 0.5% to about 20% d-limonene, from about 0.005% to about 5.0% wax and/or wax extract, from about 0.5% to about 15% monohydric alcohol, from about 0.01% to about 5.0% potassium hydroxide, and from about 0.05% to about 15% emulsifier, all by weight.
 33. The method of claim 32, wherein the monohydric alcohol is selected from the group consisting of ethanol, methanol and butanol, alone or in combination.
 34. The composition of claim 32, wherein the wax and/or wax extract comprises beeswax and/or beeswax extract.
 35. The method of claim 32, wherein the emulsifier comprises soy lecithin.
 36. The method of claim 32, wherein the plant is a member of the citrus species.
 37. The method of claim 36, wherein the disease is citrus canker.
 38. The method of claim 32, wherein the disease is caused by any species of Xanthomonas. 